I have personally got a small rock to the head and almost died.
It is about the accuracy and how fast can the other person react or protect themselves. I would say that guns like these exceed the throwing of rock with high numbers. You can also do it many times in a short duration.
Fireguns are effective for that particular reason. They are accurate, and there is no way to protect against, as they are very fast to use. And you are not limited to single throw.